Embodiments of the invention relate generally to cyclotrons, and more particularly to cyclotrons used to produce radioisotopes.
Radioisotopes (also called radionuclides) have several applications in medical therapy, imaging, and research, as well as other applications that are not medically related. Systems that produce radioisotopes typically include a particle accelerator, such as a cyclotron, that accelerates a beam of charged particles and directs the beam into a target material to generate the isotopes. The cyclotron uses electrical and magnetic fields to accelerate and guide the particles along a spiral-like orbit within an acceleration chamber. When the cyclotron is in use, the acceleration chamber is evacuated to remove undesirable gas particles that can interact with the accelerated particles. For example, when the accelerated particles are negative hydrogen ions (H−), hydrogen gas molecules (H2) or water molecules within the acceleration chamber can strip the weakly bound electron from the hydrogen ion. When the ion is stripped of this electron it becomes a neutral particle that is no longer affected by the electrical and magnetic fields within the acceleration chamber. The neutral particle is irretrievably lost and may also cause other undesirable reactions within the acceleration chamber.
To maintain the evacuated state of the acceleration chamber, cyclotrons use vacuum systems that are fluidicly coupled to the chamber. However, conventional vacuum systems may have undesirable qualities or properties. For example, conventional vacuum systems can be large and require extensive space. This may be problematic, especially when the cyclotron and vacuum system must be used in a hospital room that was not originally designed for using large systems. Furthermore, existing vacuum systems typically have several interconnected components, such as a number of pumps (including different types of pumps), valves, pipes, and clamps. In order to effectively operate the vacuum system, it may be necessary to monitor each component (e.g., through sensors and gauges) and to individually control some of these components. Furthermore, with several interconnected components there may be more interfaces or regions where leaks may occur due to damaged or worn-out parts. This may lead to costly and time-consuming maintenance of the vacuum system.
In addition to the above, conventional vacuum systems may use diffusion pumps. For example, in one known vacuum system, several diffusion pumps are fluidicly coupled to the acceleration chamber. The diffusion pumps use a working fluid (e.g., oil) to generate a vacuum by boiling the oil to a vapor and directing the vapor through a jet assembly. However, the oil within the diffusion pumps may backstream into the acceleration chamber of the cyclotron. This may reduce the vacuum system's ability to remove the gas particles, which, in turn, may negatively affect the efficiency of the cyclotron. Furthermore, oil within the acceleration chamber may induce electrical discharges that damage the electrical components used by the cyclotron to create the electrical field.
Accordingly, there is a need for improved vacuum systems that remove undesirable gas particles from the acceleration chamber. There is also a need for vacuum systems that require less space, require less maintenance, are less complex, or are less costly than known vacuum systems.